Mike Silvers, CPRC, Silvers Systems Inc. & FRSA Director of Technical Services
On any given day, I take several calls from contractors looking for advice on installation and code requirements.
One question that is being asked frequently is how many nails should I be using when installing shingles in a particular location?
There are circumstances where the answer is pretty simple. If you are in the High-Velocity Hurricane Zone (HVHZ), which includes Miami-Dade and Broward counties, or if you use a Notice of Acceptance (NOA) for your permit submittal, you need to follow Roofing Application Standard (RAS) 115. The Florida Building
Code (FBC) Building Volume, HVHZ Section 1518.7.3.2 states: Asphaltic shingles shall be installed in compliance with product approval, but in no case less than six approved roofing nails or approved fastening devices ... Remember you must comply with ALL of the requirements of RAS 115 if you're using an NOA.
If your job is located outside the HVHZ and you are using a Florida Product Approval (PA) the answer is considerably more complex. FBC, Building Volume, Section 1507.2.7 Attachment states: Asphalt shingles shall have the minimum number of fasteners required by the manufacturer and Section 1504.1. Asphalt shingles shall be secured to the roof with not less than four fasteners per strip shingle. 1504.1 Wind resistance of roofs states: Roof decks and roof coverings shall be designed for wind loads in accordance with Chapter 16 (Structural Design) and sections 1504.2, 1504.3 and 1504.4. (These three sections do not apply to shingles). Chapter 16 does contains wind maps that indicate the wind speeds for different areas of the state, but nothing specific to shingle fastening. So that brings us back to: Asphalt shingles shall have the minimum number of
fasteners required by the manufacturer. Simple enough right? Not so much.
One great thing about shingles is that we all know how to find the manufacturer's installation instructions. Roll a bundle of shingles over and they are right there. They are very often even in several languages. But when it comes to the number of fasteners needed and their placement it gets very convoluted. These instructions will usually include an application drawing named something similar to: Standard Nailing Pattern (or four-nail pattern) showing a nailing pattern with four nails. It may also contain another drawing named something similar to: Enhanced Nailing Pattern (or six-nail pattern) showing a nailing pattern with six nails. What manufacturer's installation instructions don't tell us is when (outside of the HVHZ) the additional fasteners should be used.
The shingles (material) have to meet wind resistance classifications shown in Table 1507.2. 7.1 of the FBC Building (shown above). The table shows ASTM D3161 and includes wind speeds (Vasd) of 130, 140 and 150
where Class H shingles are required, but still there is nothing on the number of nails required.
So, outside of the HVHZ, a nailing pattern using four nails should meet the minimum requirements of the code.
I wrote "should" because many building departments expect to see six nails. If a local jurisdiction is requiring six nails it should be by way of a Local Technical Amendment that is supposed to be reported to the Florida Building Commission. This should be done so it can be reviewed during the Triennial Code adoption process for possible inclusion in the code. There is currently only one local amendment being reviewed by the Roofing Technical Advisory Committee this cycle; it involves mechanical equipment. If there are local requirements dealing with shingle attachment they should have been submitted for consideration. If not, they should expire or may already have expired.
Another thing to consider is what is required by manufacturers' warranties when it comes to wind resistance?
Many of the warranties require the installer to use the enhanced (six nail) pattern to comply with the manufacturer's maximum wind speed resistance warranty (usually 130 mph). Wouldn't it make sense to make areas that require a Class H shingle or where wind speeds exceed 110 mph to also meet the six nail installation instructions? Even if using four nails complies with the minimum requirements of the code, it is clear that manufacturers know that additional fasteners help resist wind uplift. If not, why make it a warranty requirement? Our industry knows that additional fastening in almost every case improves wind uplift resistance. Why shouldn't this be true for shingles?
If all of this is confusing to roofing contractors and building officials, think about the consumer who thinks they are getting a wind resistant roof covering. Try explaining that enhanced nailing is not required by the building code, but is required by the manufacturer's warranty. Hopefully, it's not after a 120 mph high wind event that is not covered under their new roof warranty because the contractor used four nails.
Considering all of the very legitimate concerns for wind resistant structures and roof coverings, something this simple seems like a no-brainer. It's only a couple more fasteners, right? But the fact is that six nails instead of four represents 50 percent more fasteners and adds cost. A contractor who is good at sales should be able to convince a consumer that using six nails is a reasonable upgrade when you present them with the option or when you stress your standard is better than the minimum requirement approach. This is more difficult if you're roofing a new multiple building complex or development. The unsuspecting owner will never get the choice. Unfortunately on large volume projects, cost considerations usually prevail.
We need to correct this issue through the code process, better manufacturer requirements and instruction, and very possibly through better test methods. In the meantime, I recommend that you ask your manufacturer's
representative what they require, not only for code compliance but also for their warranty. You are the customer, let them know what a precarious position they've put you in. Ask the building official what they require and if they tell you six nails are needed, ask what requirement they are citing. Hopefully they can share it with you, your competition and the Commission. We know it is better, so try to include the enhanced nailing requirements in your work. It's not only the building, but your reputation you'll be protecting.
Mike Silvers, CPRC is owner of Silver Systems Inc., and is consulting with FRSA as Director of Technical Services. Mike is an FRSA Past President, Life Member, and Campanella Award recipient and brings over 40 years of industry knowledge and experience to FRSA's team.
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